Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 61,517	$ 43,181
Other comprehensive income (loss):
Unrealized gain (loss) on interest rate swaps	1,852	(820)
Other comprehensive income (loss), before income taxes	1,852	(820)
Income tax (expense) benefit	(687)	303
Other comprehensive income (loss), net of income taxes	1,165	(517)
Comprehensive income	$ 62,682	$ 42,664